In the early days of television, most programs were live or optically recorded (kinescoped) on conventional motion picture film. In such cases, no editing was required. In some cases, a program was recorded on motion picture film and conventional motion picture techniques for editing and synchronizing the sound and visual tracks could be used.
Technological advances in the art of recording video information have increased the desirability of recording television programs on video tape directly. This requires that the video be edited to provide the desired visual effect and also that a sound track be prepared in which the sound effects and dialogue are exactly synchronized with the recorded video.
In recording on video tape, it is common practice to record a time code identifying each recorded frame on the tape medium. The standard time code used in the United States (and other countries which have 30 frame NTSC television is referred to as the SMPTE time code which comprises an 80-bit code of which 43 bits are used to identify the recording time (in hours, minutes and seconds) for each frame and the number of the frame on the tape. In countries where 25 frames per second is standard, the code is referred to as the EBU time code. The use of this SMPTE time code has enabled sophisticated computer controlled techniques for editing video signals and, currently, the editing of video tape is more efficient than the editing of motion picture film wherein various film effects must be spliced together to provide a finished product.
Despite the sophistication of currently available video editing techniques, there is a problem in synchronizing an audio track with the recorded video. As an example, in producing a video tape, it may be necessary to synchronize music tracks, dialogue tracks and tracks containing various types of sound effects. Each one of these tracks (sometimes referred to as a sound mixing element) must be prepared using a time lock system dependent on the recorded SMPTE time code so that the audio and video signals are synchronized exactly. In practice, this is a very expensive undertaking since costly computer equipment must be used to synchronize and prepare the mixing elements on a multi-track tape. Because of the expense involved in revising a recorded element or track, as a practical matter, artistic compromises frequently arise in cases where a director is partially dissatisfied with one or more of the mixing elements. Moreover, the inability of the director or editor to "feel" the visual medium with which he is working as the sound track is created diminishes the feeling of an artistic or creative contribution. All of these factors have limited the acceptance by industry of direct video recording of television programs.